Conventionally, as the light source of a lighting system for a non-luminescent and transmissive display device such as a liquid crystal display, a cold-cathode tube has been used the most, but in recent years from the standpoint of wide color reproduction and environmental considerations (mercury-free), liquid crystal panels that adopt LEDs (light emitting diodes) as backlights are increasing.
In current LEDs, since the light emitting intensity per unit is small compared to a cold-cathode tube, it is necessary to arrange a plurality of LEDs in a lighting system in order to obtain the desired brightness. Here, when a plurality of LEDs are arranged uniformly in a lighting system, and all the LEDs are lighted with the same drive conditions (crest value of the drive current and drive current panel width being the same), the brightness of the light emitting surface of the lighting system becomes darker near the edges compared to the center portion. This is because the cumulative light quantity decreases the further toward the edge.
Therefore, with the object of making the brightness of a light emitting surface of a lighting system uniform at the center and the edges, an LED arrangement format known as a so-called side-lamp type has conventionally been proposed (for example, refer to Patent Document 1). Here, FIG. 7 is a schematic perspective diagram that shows a liquid crystal panel unit (90) according to a conventional example in which the side-lamp type is adopted. In the liquid crystal panel (90), optical films (92), a light guide plate (93) and a reflecting plate (94) are arranged on the rear surface of a liquid crystal panel (91), with a substrate (95) of an LED back array (side-lamp type) in which LEDs (not shown) are arranged in a linear manner at a fixed interval being disposed so as to extend along the edge of the light guide plate (93).